Centuries later, the animals from Brave that have been experimented on by the witch have interbred, creating a large-scale population of animals slowly gaining personification and intelligence on their own.

There are two progressions: the progression of the animals and the progression of artificial intelligence. The events of the following movies set up a power struggle between humans, animals, and machines.

The stage for all-out war in regards to animals is set by Ratatouille, Finding Nemo, and Up, in that order. Notice I left out A Bug’s Life, but I’ll explain why later.

One of the dinosaurs from The Good Dinosaur shows up in Inside Out, a Monsters Inc. character is pictured in Brave, a Lightning McQueen toy is in Toy Story 3, a moped from Ratatouille is in Wall-E’s junkyard, etc. etc. This is a perfect bit of superfan trolling from the Pixar team. Kudos.